Circuit breaker with undervoltage tripping means



B. A. PITEO, JR, ETAL 2,912,544

a MEANS Nov. 10, 1959 CIRCUIT BREAKER WITH UNDERVOLTAGE TRIPPIN FiledOct. 23, 1958 2 Sheets-Sheet 1 k W T O L -nn r m3 M M M A m M E Y B Nov.10, 1959 B. A. PlTEO, JR., ETA]. 2,912,544

CIRCUIT BREAKER WITH UNDERVOLTAGE TRIPPING MEANS Filed Oct. 23. 1958 2Sheets-Sheet 2 INVENTORS BENJAMIN A. Fn'zo JR.,

DAVID B. Powzu.

BY I

ATTORNEY CIRCUIT BREAKER WITH UNDERVOLTAGE TRIPPING lVflilANS BenjaminA. Piteo, Jr., Forestville, and David B. Powell, Bristol, Conn.,assignors to General Electric Company, a corporation of New YorkApplication October 23, 1958, Serial No. 769,112 6 Claims. (Cl. 200-106)Our invention relates to electric circuit breakers, and particularly toelectric circuit breakers incorporating means for causing automaticopening of such circuit breaker upon the occurrence of low voltage orundervoltage conditions. 7

Electric circuit breakers of the type comprising a molded insulatingcasing, ordinarily incorporate means for causing the contacts of thecircuit breaker to open automatically upon the occurrence of high orexcessive current conditions in the circuit. Thus, operating mechanismis provided including a latch member and a trip member normallyrestraining the latch member and arranged so that upon movement of thetrip member by a current responsive means, the latch member is releasedand the automatic circuit breaker mechanism opens the contacts. The tripmember is ordinarily actuated by a.

current responsive member such as a bimetallic strip or a magneticoperating means. In addition, it is often desirable to provide in suchcircuit breakers auxiliary tripping means to cause the automatic openingof such circuit breaker not only upon the occurrence of excessivecurrent conditions in the circuit, but also upon the occurrence ofcertain other electrical conditions, such as the occurrence of unusuallylow voltage conditions in the circuit. In accordance with the prior art,magnetic solenoid-type devices have been provided which are normallyclosed and which are released upon theoccurrence of undervoltageconditions and moved by spring means to actuate the tripping device tocause tripping of the circuit breaker. Such devices have, however, beenrelatively large, bulky, and expensive. Such prior art devices have alsonot been suitable for installation by the user, but have requiredinitial installation by the manufacturer of the basic circuit breakerbecause of the necessity for mounting different parts and adjusting themwith relation to other parts of the breaker mechanism and to each other.

It is an object of the present invention to provide an electric circuitbreaker incorporating an undervoltage tripping device which is small andinexpensive, and which can be readily added to a conventional circuitbreaker construction by the user.

It is another object of the invention to provide a basic construction,the major parts of which are readily adaptable for use with circuitbreakers having tripping devices of the push-type as well as of thepull-type.

In accordance with the invention, there is provided an electric circuitbreaker comprising an insulating casing, at least two relatively movablecontacts, operating means for operating the movable contacts betweenopen and closed position and including a trip member movable to causeautomatic opening of such contacts, and undervoltage trip meanscomprising a supporting bracket carrying a magnetic core member andmounted in relatively fixed vrelation within the housing. A movablearmature is supported on the core member and is biased for movernentaway from the core .member.

The armature also has an extension engageable with the trip member toUnited States Patent 2,912,544 Patented Nov. 10, 1959 ICC ' armature onthe occurrence of low voltage conditions.

Means is also provided for subsequently reclosing the armature uponautomatic opening movement of the contacts, to restore the initialimpedance of the device and prevent its burning out. This means, inaccordance with the invention, comprises an operating member carried bythe main supporting bracket which is engaged and operated by aprojection carried by the contact cross arm of the circuit breaker toreclose the armature. This operating projection, moreover, is relativelyclosely adjacent the pivot point of the contact arm of the circuitbreaker, whereby a high amount of force is made available .for resettingthe armature, and the use of complicated inter connecting linkages isavoided.

- The invention will be better understood by reference to the followingdetailed description, taken in conjunction with the accompanyingdrawings, and its scope will'be pointed out in the appended claims.

In the drawings:

Figure l is a side elevation view of a portion of an electric circuitbreaker incorporating the invention, a portion of the side wall beingbroken away;

Figure 2 is'a side elevation view of a portion of the mechanism ofFigure 1 showing the parts in a different position;

Figure 3 is a view similar to Figure 2 but showinga different form ofthe invention, adapted for use with In accordance with the invention asshown in Figure 1,

an electric circuit breaker is provided comprising an insulating casing10 containing a plurality of relatively stationary contact assemblies11, only one of which is shown, and a plurality of relatively movablecontact assemblies 12, only one of which is shown, pivotally supportedin the casing 10 on a pivotal axle 13. The movable contact assembliesare ganged together, for movement in unison, by a contact cross armmember 14 rigidly attached to each of the contact arms by suitable meanssuch as by inverted U-shaped brackets 15, the movable contacts areconnected by suitable means, such as by a flexible braid 16A, to oneterminal 17A of a trip unit 17 which has its other terminals 17Bconnected to relatively stationary terminal connecting lugs 19 forconnection to incoming power lines.

The trip unit 17 includes a movable trip member '20 which is pivotallysupported at 21 in the trip unit casing, and which is movable bysuitable current responsive means, not shown, contained within the tripunit 17, to cause release of a mechanism retaining latch, not shown, andto cause automatic opening of the circuit breaker contact inconventional manner.

A manually engageable handle 22 is also provided for manually operatingthe mechanism to move the contacts between open and closed positions.The trip unit construction and the construction of the operatingmechanism for the circuit breaker contacts may be of any suitable type.For convenience, the present invention has been shown in Figures l-3 asincorporated in a circuit breaker of the type disclosed in applicationsSerial Number 679,- 606, Steven and Marshall, and 679,607, Judd andYoung, filed August 22, 1957, and assigned to the same assignee as thepresent invention.

a open position to its closed position.

i 3 For the purpose of causing actuation of the trip member 20 upon theoccurrence of predetermined low voltage conditions in the circuit or inany predetermined circuit,

undervoltage trip means is provided, comprising, referring particularlyto Figures 1 and 2, a stationary supporting bracket 23 rigidly attachedto the insulating housing of the trip unit 17 by suitable means such asby screws 24. The

bracket 23 includes a portion 25 which extends around and serves tosupport a generally U-shaped magnetic core lamination assembly 26, towhich it is attached by suitable means such as by rivets 27. TheU-shaped core portion -26 of the device also carries on one leg thereofthe energizing coil 29 provided with leads 30 for connection to .asuitable power source.

The form of the invention shown in Figure 1 is especially adapted forusewith alternating current control power sources.

The magnetic core portion 26 carries a non-magnetic slidable bracket 31on the leg thereof opposite the winding 29. The assembly 31 is slidablysupported by means of pins 32 rigidly carried by the magnetic coreportion 26 and extending through corresponding slots 33 in the bracket31.

The sliding bracket 31 carries a movable armature member 35, which ispivotally supported thereon by means of pivot pin 36. The armaturemember 35 is adapted to bridge the pole portions of the U-shaped coreassembly 26 when the device is in its energized condition. Slidingbracket 31 is constantly biased toward the open position by means of atension spring 31A which has one end anchored to the pin 32 at the rightof the assembly and has the other end thereof hooked into the slot 33 atthe other end of the assembly. A generally hook-shaped extension 37 isattached to the bight portion of bracket 31 and is disposed and arrangedto engage the trip member 20 when the bracket assembly 31 moves to theright,

- causing tripping of the circuit breaker mechanism.

In order to minimize the size and cost of the undervoltage tripassembly, it is desirable that the magnetic assembly be called upon onlyto retain the armature 35 in its closed position against the bias of thespring 36, and that it not be required to move the armature from its Inorder to make this possible, and also to prevent overheating of the coilif left in the open condition, there is provided, in accordance with theinvention, means for automatically reclosing the armature 35 to theposition indicated in Figure 1 upon movement of the contact arm 16 toits open circuit position.

For this purpose, the bracket 25 is provided with an extension 38extending from the bight portion thereof, and an operating lever 39 ofinsulation material is pmally supported on the extension 38 and extendsbe-- tween the sides of the bracket member 31 adjacent the support ofthe hook portion 37. The contact arm 16 is also provided with anextension 40 attached to the contact arm by suitable means such as byrivet 41 and having its end portion disposed and arranged to engage theoperating member 39 when the contact arm 16 moves to its open circuitposition.

.In Figure 2 there is illustrated the transient position which the partsassume immediately upon the occurrence 1 of an undervoltage condition inthe circuit to which the nism, not shown. The contact arms thereuponmove to the open circuit position as indicated in dotted lines in Figure2, causing the extension 40 to engage the member 39 and return it to theposition shown in dotted lines. Movement of the member 39 to itsoriginal, dotted line,

position, carries the bracket member 31 to the original or reclosedposition.

It will be observed that the construction provided is extremely compactand simple to mount and assemble and all the moving parts necessary arecarried by a common support, that is, frame member 23.

In the form of the invention shown in Figure 3, there is shown a formespecially adapted for use with direct current circuits. In this form ofthe invention, a bracket 43 is provided for mounting on the trip unithousing 17 in a manner similar to the bracket 23 of the form of Figures1 and 2. The bracket 43 has an insulating portion 51 which serves tosupport a solenoid comprising a stationary core portion 45 and a movableplunger portion 46 which is normally biased to the right as viewed inthis figure by means of a compression spring 47. The plunger 46 has anextension shaft 48 which carries a hook-shaped member 49 similar to themember 37 of the form of Figures 1 and 2 and disposed to engage andactuate the trip member 20 in the manner similar to that described forthe form of Figures 1 and 2. For the purpose of providing for resettingand reclosing of the solenoid in this form, an actuator 50 is providedsimilar to the actuator 39 of the form of Figures 1 and 2, pivotallysupported on a bracket 44 mounted on the solenoid by screw 44A. Theextension 40 attached to the contact arm 16 serves to engage the end ofthe operating member 50 upon tripping of the circuit breaker mechanism,and restores the solenoid to its normal position when the contact armmoves to open position as illustrated in the dotted line position of thecontact arm.

In both the forms of Figures 1 and 2 and that of Figure 3, the operatingmembers 39 and 50, respectively, are preferably constructed of materialwhich, while essentially rigid has a degree of flexibility to permit anamount of overtravel to ensure seating of the armature member in itsproper location upon movement of the contact arm to open circuitposition.

In Figures 4-6, the invention is shown as applied to circuit breakersincorporating a trip bar which moves in a direction away from theoperating mechanism to cause tripping, as contrasted to the form ofFigures 1-3 in which the trip member moves toward the operating memberto cause tripping. In these forms it will be observed that theundervoltage trip device must operate to push the trip member, ratherthan to pull it.

In accordance with the form of the invention shown in Figure 4, there isprovided a circuit breaker having a casing 55 including relativelystationary contacts 56, only one shown, and relatively movable contacts57, only one I shown, mounted on a movable contact arm 58 which ispivotally supported on a stationary pivotal support 59. The contact armsof each of the poles are ganged together by means of a common contactcross arm 60. The movable contact 57 is flexibly supported on thecontact arm 58 on pivot point 61 and is normally biased away from thecontact arm 58 by means of a compression spring 62, a retaining bracket63 being provided to limit the movement of the contact member 57 awayfrom the contact arm 58. The circuit breaker also includes a trip unitindicated generally at 64, which includes a trip member 65 pivotallysupported at 66 and movable in a direction away from the operatingmechanism to cause tripping of the circuit breaker.

The circuit breaker is also provided with suitable operating mechanism,not shown, which is operable by For the purpose of causing actuation ofthe trip member 65 upon the occurrence of predetermined low voltageconditions in the circuit, there is provided an electromagnetic devicecomprising a frame 68 which is rigidly attached to the trip unitinsulating casing by suitable means, not shown, and which carries arelatively sta tionary, generally U-shaped magnetic core assembly 69.The core assembly 69 carries a pair of guide pins 70 and 71 mounted infixed relation thereon and extending therethrough with portionsextending at each side of the core assembly 69. The pins 70 and 71 actas guide pins for a non-magneticguide bracket 72 which'has slots cut inthe side walls thereof corresponding to the pins 70 and 71. The guidebracket 72 also carries the movable armature portion 73 which ispivotally mounted thereon by means of a pin 74, and includes anextension 75 for actuating the trip member 65. The bracket 72 and itsmovable armature 73 are constantly biased toward the left-hand position,that is, the open position, by the action of tension springs 76 whichhave one end thereof anchored on the pin 70 and have the other endthereof engaging with bracket 72 in the slots corresponding to the pins71. It will be observed, therefore, that so long as the core of themagnetic assembly 69 remains energized and holds the armature member 73in the position shown, the breaker will not be actuated. Upon thedecrease of voltage in the energizing coilhowever, the armature isimmediately released and the action of the springs 76 moves the armatureand its carrier 72 to the left causing the extension 75 to engage thetrip member 65 to cause tripping of the circuit breaker.

For the purpose of resetting the undervoltage trip device, a reset lever78 is provided, which is pivotally mounted by means of a pivot pin 79 onan extension of the frame member 68. The lever member 78 carries aplunger 80 at one end thereof disposed adjacent a bight portion of thebracket 72. The plunger 80 is slidable in the end of the lever 78 and isspring biased to a normally projecting position as shown in Figure 4.

Upon decrease of voltage in the energizing coil of the magnetic member,the armature member 73 is released, as described above, and movestemporarily to the intermediate position indicated in Figure in whichthe plunger member 75 engages the trip member 65 to cause tripping.Immediately upon the opening of the contacts, the contact arm 58 movesto the position indicated in dotted lines in Figure 5, causing thecontact cross arm 60 to engage the lower portion of the lever 78,rotating the lever 78 clockwise. Clockwise rotationof the lever 78causes the plunger 80 to engage the bight portion of the bracket 72thereby sliding the bracket 72 and the movable armature 73 back to theirreclosed or reset position.

The plunger 80 is slidably mounted and biased by a spring to a normallyprojecting position to allow a certain amount of travel of the lever 78with respect to the armature 73 to ensure positive reclosing and holdingof the armature in closed position until the circuit breaker isreclosed.

In Figure 6 there is shown a further embodiment of the invention alongthe lines of Figures 4 and 5 that is adapted to cause actuation of atrip member by a pushing action, but especially adapted for DC.applications. In this form of the invention, a plunger-type solenoid isprovided having a stationary magnetic portion 82 and a movable magneticplunger portion 83 which is normally biased by a compression spring 84toward projecting position with respect to the stationary portion 82. Asuitable coil 85 is also provided for energizing the magnetic component.The plunger portion 83 also includes an extension rod 86 adapted toengage the trip member 65. The core and coil assembly is supported upona suitable bracket 87 rigidly attached to the trip unit housing 64 bysuitable means not shown.

Resetting of the magnetic armature or plunger portion is accomplished inthis form in the same manner as indicated in Figure 5 by means of lever78 which is pivotally mounted at 79 on the frame portion 87 and theplunger portion 80 of the lever 78 is disposed to engage the plungerportion 83 when the lever 78 is rotated clockwise by means of the crossarm 60 when the contact arm 58 moves toward open circuit position uponthe occurrence of tripping of the circuit breaker.

It will be observed that while four diiferent forms of the invention areshown, all such forms of the invention utilizes a portion of the contactcross arm engaging a pivotally supported lever member to cause resettingof the magnetic member upon the occurrence of tripping of the circuitbreaker. All forms, also, include the provision, in such pivoted member,of resilient means for permitting a certain amount of overtravel of theactuating means with respect to the actuated means.

While only particular embodiments of the invention have been disclosed,it will be readily apparent that many modifications thereof may be madeby those skilled in the art. It is therefore intended by the appendedclaims to cover all such modifications as fall within the true spiritand scope of the invention.

What we claim as new and desire to secure by Letters 7 Patent of theUnited States is:

1. In an electric circuit breaker having a contact arm movable betweenopen and closed circuit positions and a member movable to causeautomatic opening movement of said contact arm, an undervoltage tripdevice comprising a relatively stationary magnetic core member, arelatively movable magnetic armature member, said armature being movablebetween a normal position in engagement with said core member and areleased position out of engagement with said core member, means forreturning said armature member from said released to said normalposition upon the movement of said contact arm from closed to openposition comprising an elongated lever pivotally mounted on a fixedpivot in said circuit breaker, means carried by said contact arm forengaging said lever to rotate said lever about said pivot, and meansconnecting said lever and said movable armature for causing reclosingmovement of said armature upon contact opening movement of said contactarm.

2. The invention as set forth in claim 1 wherein said pivotal levercomprises resilient means for transmitting force from 'said contact armto said movable armature whereby to permit a small amount of overtravelof said contact arm following engagement of said armature with said coremember.

3. In an electric circuit breaker, a contact arm movable between openand closed circuit positions, a movable trip member movable to causeautomatic opening movement of said contact arm, an undervoltage tripdevice comprising a relatively stationary magnetic core member, arelatively movable armature member, said core member being between saidtrip member and said armature, means carried by said armature forengaging said trip member upon movement of said armature in a directionaway from said core member, means for returning said armature intoengagement with said core member comprising an elongated lever pivotallysupported on a pivot stationary relative to said core member, aprojection carried by said contact arm adjacent said pivot, said leverhaving an end portion disposed in the path of movement of saidprojection, and a connection between an intermediate part of said leverand said movable armature to return said armature to reclosed positionupon movement of said contact arm to contact open position.

4. The invention as set forth in claim 3 wherein said pivoted levercomprises a relatively wide, thin, flat strip of insulating materialhaving a substantial amount of inherent resilience.

5. An electric circuit breaker comprising a contact arm movable betweenopen and closed circuit positions and a movable trip member movable tocause automatic of said contact arm and its other end portion disposedto engage said movable armature member to return said armature memberinto contact with said magnetic core member upon movement of said firstend by said contact 6. An electric circuit breaker as set forth in claim5 wherein' said pivoted member also includes a projecting plungeractuator, said plunger being biased outwardly of said lever bycompression spring means whereby to provide resilient means fortransmitting force from said contact arm to said movable armaturewhereby said contact arm may overtravel a small amount after engage- 10ment of said armature with said core member.

References Cited in the file of this patent UNITED STATES PATENTS SandinApr. 18, 1939 Slebodnik Dec. 14, 1954

